Finally under certain conditions, Tagetes may be viewed as a weed. Khaki weed (T. minuta) is a common weed species in peanut fields in South Africa and is a host of potato rot nematode, Ditylenchus destructor, which is an important peanut pest (Jones and De Waele, 1988). De Waele et al. (1990) found that D. destructor can survive on T. minuta when peanut is not grown. Although T.minuta is not a good host, D. destructor increased to larger numbers in hulls and seeds of peanut grown after T. minuta, suggesting that it can survive on this weed in the absence of the peanut host. However, T. minuta was shown to be a poor host for Pratylenchus zeae and its root residues were reported to suppress P. zeae (Jordaan and De Waele, 1988), which is the most common plant-parasitic nematode species associated with maize in South Africa (De Waele and Jordaan, 1988). In addition, T. minuta was reported to also suppress Pratylenchus brachyurus (Good et al., 1965), another commonly occurring lesion nematode.Despite its positive benefits with respect to nematode suppression, the integration of marigold into nematode pest management programs is practically nonexistent in commercial farm operations. This might be partially due to the limited economic value of marigold for ecosystem services other than nematode repression. Furthermore, marigold is mostly marketed as an ornamental plant and seeds are costly compared with cover crop seeds. If more marigold seeds were to be commercialized for cover cropping, seed costs would be more affordable. Still, the failure of information dissemination to farmers is probably most contributable to the lack of awareness and associated use of marigold. Thus, we hope this review will bring additional notice to marigold resulting in greater use and more research effort.
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